Messages in this thread Patch in this message | | | From | Rasmus Villemoes <> | Subject | [PATCH 22/22] x86_64: use relative pointers with dynamic debug | Date | Thu, 20 Sep 2018 00:04:44 +0200 |
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Similar to how x86_64 uses bug_entry-relative pointers to reduce sizeof(struct bug_entry), the same thing can now be done for struct _ddebug, saving 16 bytes for each of those (i.e., each pr_debug, dev_dbg etc. in a CONFIG_DYNAMIC_DEBUG kernel).
Note the use of .ifndef/.endif in asm to avoid
fs/aio.c:1382: Error: symbol `__UNIQUE_ID_ddebug112' is already defined
This is due to uses of pr_debug et al in functions that get inlined. In such a case, __COUNTER__ is obviously only expanded once, but the asm() is repeated once for every inlined instance. Letting all instances share the same descriptor object is the right thing to do; that is also what happens when it is the compiler that defines a static object inside an inline(d) function.
Cc: x86@kernel.org Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> --- arch/x86/Kconfig | 1 + arch/x86/include/asm/dynamic_debug.h | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 36 insertions(+) create mode 100644 arch/x86/include/asm/dynamic_debug.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 1a0be022f91d..a44168930e52 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -90,6 +90,7 @@ config X86 select CLOCKSOURCE_WATCHDOG select DCACHE_WORD_ACCESS select DMA_DIRECT_OPS + select DYNAMIC_DEBUG_RELATIVE_POINTERS if X86_64 select EDAC_ATOMIC_SCRUB select EDAC_SUPPORT select GENERIC_CLOCKEVENTS diff --git a/arch/x86/include/asm/dynamic_debug.h b/arch/x86/include/asm/dynamic_debug.h new file mode 100644 index 000000000000..350ef6e2feff --- /dev/null +++ b/arch/x86/include/asm/dynamic_debug.h @@ -0,0 +1,35 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_DYNAMIC_DEBUG_H +#define _ASM_X86_DYNAMIC_DEBUG_H + +#ifdef HAVE_JUMP_LABEL +# ifdef DEBUG +# define _DPRINTK_ASM_KEY_INIT ASM_STATIC_KEY_INIT_TRUE +# else +# define _DPRINTK_ASM_KEY_INIT ASM_STATIC_KEY_INIT_FALSE +# endif +#else +# define _DPRINTK_ASM_KEY_INIT "" +#endif + +#define DEFINE_DYNAMIC_DEBUG_METADATA(name, fmt) \ + extern struct _ddebug name; \ + asm volatile(".ifndef " __stringify(name) "\n" \ + ".pushsection __verbose,\"aw\"\n" \ + "1:\n" \ + __stringify(name) ":\n" \ + "\t.long %c0 - 1b \t# _ddebug::modname_disp\n" \ + "\t.long %c1 - 1b \t# _ddebug::function_disp\n" \ + "\t.long %c2 - 1b \t# _ddebug::filename_disp\n" \ + "\t.long %c3 - 1b \t# _ddebug::format_disp\n" \ + "\t.long %c4 \t# _ddebug::flags_lineno\n" \ + "\t.long 0 \t# <padding>\n" \ + _DPRINTK_ASM_KEY_INIT \ + ".popsection\n" \ + ".endif\n" \ + : : "i" (KBUILD_MODNAME), "i" (__func__), \ + "i" (__FILE__), "i" (fmt), \ + "i" (_DPRINTK_FLAGS_LINENO_INIT)) + +#endif /* _ASM_X86_DYNAMIC_DEBUG_H */ + -- 2.16.4
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